/*
 * Copyright 2002-2018 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.web.servlet.mvc.condition;

import org.springframework.lang.Nullable;
import org.springframework.util.ObjectUtils;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.util.WebUtils;

import javax.servlet.http.HttpServletRequest;
import java.util.Collection;
import java.util.Collections;
import java.util.LinkedHashSet;
import java.util.Set;

/**
 * A logical conjunction (' && ') request condition that matches a request against
 * a set parameter expressions with syntax defined in {@link RequestMapping#params()}.
 *
 * @author Arjen Poutsma
 * @author Rossen Stoyanchev
 * @since 3.1
 */
public final class ParamsRequestCondition extends AbstractRequestCondition<ParamsRequestCondition> {

    private final Set<ParamExpression> expressions;


    /**
     * Create a new instance from the given param expressions.
     *
     * @param params expressions with syntax defined in {@link RequestMapping#params()};
     *               if 0, the condition will match to every request.
     */
    public ParamsRequestCondition(String... params) {
        this(parseExpressions(params));
    }

    private ParamsRequestCondition(Collection<ParamExpression> conditions) {
        this.expressions = Collections.unmodifiableSet(new LinkedHashSet<>(conditions));
    }


    private static Collection<ParamExpression> parseExpressions(String... params) {
        Set<ParamExpression> expressions = new LinkedHashSet<>();
        for (String param : params) {
            expressions.add(new ParamExpression(param));
        }
        return expressions;
    }


    /**
     * Return the contained request parameter expressions.
     */
    public Set<NameValueExpression<String>> getExpressions() {
        return new LinkedHashSet<>(this.expressions);
    }

    @Override
    protected Collection<ParamExpression> getContent() {
        return this.expressions;
    }

    @Override
    protected String getToStringInfix() {
        return " && ";
    }

    /**
     * Returns a new instance with the union of the param expressions
     * from "this" and the "other" instance.
     */
    @Override
    public ParamsRequestCondition combine(ParamsRequestCondition other) {
        Set<ParamExpression> set = new LinkedHashSet<>(this.expressions);
        set.addAll(other.expressions);
        return new ParamsRequestCondition(set);
    }

    /**
     * Returns "this" instance if the request matches all param expressions;
     * or {@code null} otherwise.
     */
    @Override
    @Nullable
    public ParamsRequestCondition getMatchingCondition(HttpServletRequest request) {
        for (ParamExpression expression : this.expressions) {
            if (!expression.match(request)) {
                return null;
            }
        }
        return this;
    }

    /**
     * Compare to another condition based on parameter expressions. A condition
     * is considered to be a more specific match, if it has:
     * <ol>
     * <li>A greater number of expressions.
     * <li>A greater number of non-negated expressions with a concrete value.
     * </ol>
     * <p>It is assumed that both instances have been obtained via
     * {@link #getMatchingCondition(HttpServletRequest)} and each instance
     * contains the matching parameter expressions only or is otherwise empty.
     */
    @Override
    public int compareTo(ParamsRequestCondition other, HttpServletRequest request) {
        int result = other.expressions.size() - this.expressions.size();
        if (result != 0) {
            return result;
        }
        return (int) (getValueMatchCount(other.expressions) - getValueMatchCount(this.expressions));
    }

    private long getValueMatchCount(Set<ParamExpression> expressions) {
        long count = 0;
        for (ParamExpression e : expressions) {
            if (e.getValue() != null && !e.isNegated()) {
                count++;
            }
        }
        return count;
    }


    /**
     * Parses and matches a single param expression to a request.
     */
    static class ParamExpression extends AbstractNameValueExpression<String> {

        ParamExpression(String expression) {
            super(expression);
        }

        @Override
        protected boolean isCaseSensitiveName() {
            return true;
        }

        @Override
        protected String parseValue(String valueExpression) {
            return valueExpression;
        }

        @Override
        protected boolean matchName(HttpServletRequest request) {
            return (WebUtils.hasSubmitParameter(request, this.name) ||
                    request.getParameterMap().containsKey(this.name));
        }

        @Override
        protected boolean matchValue(HttpServletRequest request) {
            return ObjectUtils.nullSafeEquals(this.value, request.getParameter(this.name));
        }
    }

}
